1. Field of the Invention
This invention relates to a fire resistant asphalt base covering more commonly referred to as asphalt shingles. The shingle is ecologically desirable because it utilizes disposable glass as a filler material.
2. Description of the Prior Art
Asphalt roofing shingles have been utilized in the building industry for many years. Such roofing shingles must meet many specifications in order to qualify for label approval. For instance, a Class A label has strict requirements relating to flame exposure, spread of flame, and burning brand. Class B requirements are less severe, and Class C requirements are still lower.
Generally, the type of shingle discussed herein comprises a felt base saturated with a bitumen and coated on at least one side with a filled asphalt coating. Fillers for asphalt coatings have varied tremendously in the past. It has been recognized that the filler can be a member of a broad group of inorganic mineral materials including carbonates, such as limestone, mica, slate flour, diatomaceous earth and other such things. Generally, this filler is finely ground for addition to the asphalt coating, but a critical particle size distribution has not been established or deemed critical in the production of the asphalt coating. Glass fillers have heretofore been used as part of the inorganic mineral filling in asphalt coatings. The glass fillers, however, have generally been of the spun glass or glass fiber type and have not in the past been used in specific amounts with a specific particle size distribution. The only attempts to use glass with other inorganic mineral fillers includes those attempts wherein glass is first fused with the other mineral material, such as a carbonate, and then broken up for addition to the asphalt coating. Singularly or in combination, all of the known prior filled asphalt coatings do not include the particular embodiment of granular glass of a particular particle size distribution or of a combination of granular glass of a particular particle size distribution with a non-glass granular mineral filler likewise of a particular particle size distribution.